Toolpath generation for a deformation based flexible manufacturing processes like incremental forming is very challenging because the sheet stock material moves as the toolpath progresses. CNC machining toolpaths work fairly well for single point incremental forming (FIG. 1a) because the features always lie below the blank/workpiece, but these toolpaths are inadequate for double sided incremental forming (“DSIF”) (FIG. 1b). DSIF uses two tools, one on either side of the blank, which makes it possible to form concave and convex features by switching which tool acts as the forming tool or the supporting tool.
In general, CNC toolpaths are not appropriate for DSIF is because embedded features have to be formed in the correct sequence to make sure the tools do not puncture the sheet stock workpiece. Existing CNC machining based tool can only generate toolpaths in one direction. In order to use the existing CNC machining module for making features on both sides of the sheet, one has to generate machining paths from two different directions, and manually sort out the forming sequence and stitch those toolpaths together.
Further, in existing technologies, the toolpath is generated from CAM software, and the following steps are performed manually by the operator of the tools: separating the toolpath contour by contour, grouping the contours into features, picking the feature forming order, reversing the toolpath for concave features, and synchronizing the tools to go from feature to feature.
The method described herein uses geometrically constructed maps to create a hierarchical structure in the form of a rooted tree to group features, which makes it possible to form features on either side of the sheet. This method sorts all the features and automatically provides a synchronized path for the supporting tool to follow the forming tool to form all the features on the part in the correct order and direction. The method permits fine control of the individual features and their process parameters, arbitrary changes to the forming order and direction of the features within the feasibility of a forming operation, and translation of each individual feature to the plane to enhance the geometric accuracy of the process.
In this method, the features in a particular geometry or object are represented as a hierarchical data structure. The hierarchical data structure of choice is a rooted tree, since it allows fine control over individual features which are represented as nodes in the tree. Tree traversal algorithms can then be used to generate toolpaths for the individual features, which allow the forming order and direction of the features to be changed accordingly.
A map is used to hold information about the relationship between features during the slicing stage of toolpath generation, because maps provide logarithmic complexity for key insertions and lookups.
The maps are then be used to build the rooted trees once all the information about the relationships between the features has been stored.
This approach is unique in its use of fundamental data structures to develop a new way of representing features in DSIF and similar processes which gives users incredible versatility and control over the toolpath generation process for complex geometries.